Laser-equipped gas reaction chamber for probing environmentally sensitive materials at near atomic scale

Numerous metallurgical and materials science applications depend on quantitative atomic-scale characterizations of environmentally-sensitive materials and their transient states. Studying the effect upon materials subjected to thermochemical treatments in specific gaseous atmospheres is of central importance for specifically studying a material’s resistance to certain oxidative or hydrogen environments. It is also important for investigating catalytic materials, direct reduction of an oxide, particular surface science reactions or nanoparticle fabrication routes. This manuscript realizes such experimental protocols upon a thermochemical reaction chamber called the "Reacthub" and allows for transferring treated materials under cryogenic & ultrahigh vacuum (UHV) workflow conditions for characterisation by either atom probe or scanning Xe(+)/electron microscopies. Two examples are discussed in the present study. One protocol was in the deuterium gas charging (25 kPa D(2) at 200°C) of a high-manganese twinning-induced-plasticity (TWIP) steel and characterization of the ingress and trapping of hydrogen at various features (grain boundaries in particular) in efforts to relate this to the steel’s hydrogen embrittlement susceptibility. Deuterium was successfully detected after gas charging but most contrast originated from the complex ion FeOD(+) signal and the feature may be an artefact. The second example considered the direct deuterium reduction (5 kPa D(2) at 700°C) of a single crystal wüstite (FeO) sample, demonstrating that under a standard thermochemical treatment causes rapid reduction upon the nanoscale. In each case, further studies are required for complete confidence about these phenomena, but these experiments successfully demonstrate that how an ex-situ thermochemical treatment can be realised that captures environmentally-sensitive transient states that can be analysed by atomic-scale by atom probe microscope

Laser-equipped gas reaction chamber for probing environmentally sensitive materials at near atomic scale

Numerous metallurgical and materials science applications depend on quantitative atomic-scale characterizations of environmentally-sensitive materials and their transient states. Studying the effect upon materials subjected to thermochemical treatments in specific gaseous atmospheres is of central importance for specifically studying a material’s resistance to certain oxidative or hydrogen environments. It is also important for investigating catalytic materials, direct reduction of an oxide, particular surface science reactions or nanoparticle fabrication routes. This manuscript realizes such experimental protocols upon a thermochemical reaction chamber called the "Reacthub" and allows for transferring treated materials under cryogenic & ultrahigh vacuum (UHV) workflow conditions for characterisation by either atom probe or scanning Xe+/electron microscopies. Two examples are discussed in the present study. One protocol was in the deuterium gas charging (25 kPa D2 at 200°C) of a high-manganese twinning-induced-plasticity (TWIP) steel and characterization of the ingress and trapping of hydrogen at various features (grain boundaries in particular) in efforts to relate this to the steel’s hydrogen embrittlement susceptibility. Deuterium was successfully detected after gas charging but most contrast originated from the complex ion FeOD+ signal and the feature may be an artefact. The second example considered the direct deuterium reduction (5 kPa D2 at 700°C) of a single crystal wüstite (FeO) sample, demonstrating that under a standard thermochemical treatment causes rapid reduction upon the nanoscale. In each case, further studies are required for complete confidence about these phenomena, but these experiments successfully demonstrate that how an ex-situ thermochemical treatment can be realised that captures environmentally-sensitive transient states that can be analysed by atomic-scale by atom probe microscope

Treatment of persistent organic pollutants in wastewater using hydrodynamic cavitation in synergy with advanced oxidation process

Persistent organic pollutants (POPs) are very tenacious wastewater contaminants. The consequences of their existence have been acknowledged for negatively affecting the ecosystem with specific impact upon endocrine disruption and hormonal diseases in humans. Their recalcitrance and circumvention of nearly all the known wastewater treatment procedures are also well documented. The reported successes of POPs treatment using various advanced technologies are not without setbacks such as low degradation efficiency, generation of toxic intermediates, massive sludge production, and high energy expenditure and operational cost. However, advanced oxidation processes (AOPs) have recently recorded successes in the treatment of POPs in wastewater. AOPs are technologies which involve the generation of OH radicals for the purpose of oxidising recalcitrant organic contaminants to their inert end products. This review provides information on the existence of POPs and their effects on humans. Besides, the merits and demerits of various advanced treatment technologies as well as the synergistic efficiency of combined AOPs in the treatment of wastewater containing POPs was reported. A concise review of recently published studies on successful treatment of POPs in wastewater using hydrodynamic cavitation technology in combination with other advanced oxidation processes is presented with the highlight of direction for future research focus

Performance Analysis of Unsupervised Clustering Methods for Brain Tumor Segmentation

Medical image processing is the most challenging and emerging field of neuroscience. The ultimate goal of medical image analysis in brain MRI is to extract important clinical features that would improve methods of diagnosis & treatment of disease. This paper focuses on methods to detect & extract brain tumour from brain MR images. MATLAB is used to design, software tool for locating brain tumor, based on unsupervised clustering methods. K-Means clustering algorithm is implemented & tested on data base of 30 images. Performance evolution of unsupervised clusteringmethods is presented

Hydrogen-induced hardening of a high-manganese twinning induced plasticity steel

High-manganese twinning-induced plasticity (TWIP) steels exhibit high strain hardening, high tensile strength, and high ductility, which make them attractive for structural applications. At low tensile strain rates, TWIP steels are prone to hydrogen embrittlement (HE). Here though, we study the hardening and strengthening resulting from electrochemical hydrogen-charging of a surface layer of a Fe-26.9Mn-0.28C (wt.%) TWIP steel. We observed a 20% increase in yield strength following the electrochemical hydrogen-charging, accompanied by a reduction in ductility from 75% to 10% at a tensile strain rate of 10−3s−1. The microstructural evolution during tensile deformation was examined at strain levels of 3%, 5% and 7% by electron backscatter diffraction (EBSD) and electron channeling contrast imaging (ECCI) to study the dislocation structure of the hardened region. As expected, the microstructure of the hydrogen-hardened and the uncharged regions of the material evolve differently. The uncharged areas show entangled dislocation structures, indicating slip from a limited number of potentially coplanar slip systems. In contrast, hydrogen segregated to the grain boundaries, revealed by the deuterium-labelled atom probe tomography, delays the dislocation nucleation by blocking dislocation sources at the grain boundaries. The charged areas hence first show the formation of cells, indicating dislocation entanglement from more non-coplanar slip systems. With increasing strain, these cells dissolve, and stacking faults and strain-induced ε-martensite are formed, promoted by the presence of hydrogen. The influence of hydrogen on dislocation structures and the overall deformation mechanism is discussed in details

Hydrogen embrittlement of twinning-induced plasticity steels: Contribution of segregation to twin boundaries

Metallic materials, especially steel, underpin transportation technologies. High-manganese twinning induced plasticity (TWIP) austenitic steels exhibit exceptional strength and ductility from twins, low-energy microstructural defects that form during plastic loading. Their high-strength could help light-weighting vehicles, and hence cut carbon emissions. TWIP steels are however very sensitive to hydrogen embrittlement that causes dramatic losses of ductility and toughness leading to catastrophic failure of engineering parts. Here, we examine the atomic-scale chemistry and interaction of hydrogen with twin boundaries in a model TWIP steel by using isotope-labelled atom probe tomography, using tritium to avoid overlap with residual hydrogen. We reveal co-segregation of tritium and, unexpectedly, oxygen to coherent twin boundaries, and discuss their combined role in the embrittlement of these promising steels

BRAIN Journal - Performance Analysis of Unsupervised Clustering Methods for Brain Tumor Segmentation

<i>Abstract</i><div><br></div><div><div>Medical image processing is the most challenging and emerging field of neuroscience. The ultimate goal of medical image analysis in brain MRI is to extract important clinical features that would improve methods of diagnosis & treatment of disease. This paper focuses on methods to detect & extract brain tumour from brain MR images. MATLAB is used to design, software tool for locating brain tumor, based on unsupervised clustering methods. K-Means clustering algorithm is implemented & tested on data base of 30 images. Performance evolution of unsupervised clustering</div><div>methods is presented.</div></div><div><br></div><div><b>Find more here:</b></div><div><b>https://www.edusoft.ro/brain/index.php/brain/article/view/420</b><br></div

Advances in Cryo-Atom Probe Tomography Studies on Formation of Nanoporous Metals by Dealloying (Digital Presentation)

The selective removal of a less noble (more chemically active) metal from a mixture of 2–3 metals can yield a bicontinuous, open-pore, 3D nanoporous metal (NPM), that is rich in the more noble metal(s)1. NPMs have been successfully developed by the intelligent use of the conventionally-undesired dealloying corrosion. The excellent properties of NPMs are attributed to the surface area-to-volume ratio, and high curvature of nanoligament surfaces 2,3 . Experimental work on NPMs revealed the formation of uniformly nanoporous structure by dealloying AgAu alloy in nitric acid, a method still widely used until today for making nanoporous gold (NPG). This dealloying process is complex: the selective dissolution of the less-noble element should lead to the creation of surface vacancies or adatoms, which migrate across the surface to form surface roughening features, and thus assisting the migration of the residual more-noble atoms, leading to island growth4. Ex-situ characterization cannot fully explain some intricate details at the dealloying interface and at the surface of the formed nanoligaments. Gaining insight into initial stages of dealloying, and the inherent competition between surface roughening from the dissolution of silver atoms, and surface smoothening from surface diffusion of gold atoms5, can only be done effectively by monitoring the changes occurring at the surfaces of alloys in-situ. Several notable in-situ methods were used to characterize formation of NPMs, such as TEM 6, often limited by the 2D nature of the analysis. Also, synchrotron-based methods such as X-ray nanotomography 7 and neutron scattering 8 were limited by resolution and lack of compositional contrast. APT is a powerful technique that provides 3D characterization9 and near-atomic-scale compositional analysis of materials, and could complement the abovementioned suite of techniques, yet the analysis of nanoporous structure comes with challenges. Aiming to develop a universal method for probing corrosion systems by APT, the concept of embedding frozen solutions in corroded systems was developed and reported in a recent reporting 10 of analyzing NPMs along with frozen water-based solutions. This involved the joint use of an ensemble of equipment and techniques that connect the frozen liquid to the atom probe, including a plasma-focused ion beam (PFIB) where the preparation of APT specimens uses a cryostage, and transfer of the frozen sample through ultra-high-vacuum suitcase11. This paved the way for many advances in characterization of corrosion processes, as the possibility of freezing corrosion reactions for APT (now known as cryo-APT) arises. Here, we further develop cryo-APT to probe into the mechanisms of dealloying in AgAu and how that leads to the formation of NPG using our in-situ approach. Nanoligament structure will be correlated with dealloying conditions by making observations at the solid-liquid interface in 3D. References Newman, R. C. 2.0

BRAIN Journal-Performance Analysis of Unsupervised Clustering Methods for Brain Tumor Segmentation-Figure 1. Diagnosis Rate in different Countrie

<p>In MRI images, the amount of data is too much for manual segmentation. The procedure is<br> tedious, time, labor consuming, subjective and requires expertise. This gave way to methods that are<br> computer-aided with user interaction at varying levels. These methods are automatic and objective<br> and the results are highly reproducible. We designed software tool for locating brain tumor, based<br> on unsupervised clustering methods and analyzed its performance</p